β‐Sitosterol attenuates anlotinib resistance in non‐small cell lung cancer cells by inhibiting miR‐181a‐3p/SHQ1 signaling

Abstract

Anlotinib is used for the treatment of advanced non‐small cell lung cancer; however, the emergence of drug resistance limits its clinical application. β‐sitosterol may also be used to treat lung cancer, but there have been no studies evaluating β‐sitosterol against anlotinib‐resistant lung cancer. The purpose of this study was to determine the mechanism by which β‐sitosterol enhances the sensitivity of lung cancer cells to anlotinib. A549 cells were treated with different concentrations of anlotinib to generate anlotinib‐resistant cells (A549/anlotinib cells). miR‐181a‐3p mimics were transfected into A549/anlotinib cells. A549 and A549/anlotinib cells were treated with β‐sitosterol at various concentrations. The Cell Counting Kit‐8 (CCK‐8) assay was used to measure cell proliferation. Apoptosis was assessed by flow cytometry. Real‐time quantitative PCR was used to measure the expression of miR‐181a‐3p. The interaction of miR‐181a‐3p with the H/ACA ribonucleoprotein assembly factor (SHQ1) was predicted using the miRDB and TargetScan Human databases and verified with a luciferase reporter assay. The expression of SHQ1, activating transcription factor 6 (ATF6), and glucose‐regulated protein 78 (GRP78) were measured by western blot analysis. β‐Sitosterol effectively suppressed A549/anlotinib cell proliferation and promoted apoptosis. SHQ1 is a downstream target of miR‐181a‐3p. The expression of miR‐181a‐3p was inhibited; however, SHQ1 expression was increased by β‐sitosterol treatment of A549/anlotinib cells. The inhibition of SHQ1, ATF6, and GRP78 protein expression by β‐sitosterol in A549/anlotinib cells was rescued by increased miR‐181a‐3p. β‐Sitosterol markedly promotes anlotinib‐resistant A549 cell apoptosis and inhibits cell proliferation by activating SHQ1/UPR signaling through miR‐181a‐3p inhibition.